1. Field of the Invention
This invention is directed to resins made from rosin, fatty acid, phenolic compound and aldehyde, where the resins are particularly useful in inks for lithographic and gravure printing.
2. Description of the Related Art
The use as a major component in the preparation of binders for printing inks is very well known in the art. Such rosin-based inks are used for a wide variety of printing processes, including flexography, gravure printing, letterpress printing, and lithography. Each printing process requires an ink with properties specific for optimal usage of that particular process, where relevant ink properties include viscosity, solvent evaporation, wettability, pigment dispersion, and compatibility with the other materials composing the ink press. In order to use rosin in inks having such diverse range of necessary performance properties, it is very important to select the appropriate materials to react with the rosin to form the ink binder. See, e.g., Roger F. Burke, “Rosin-based Printing Inks,” Naval Stores, Chapter 19, Pulp Chemicals Association (1989),
The following references describe some of the rosin-based phenolic resins known in the art.
U.S. Pat. Nos. 6,172,174 (2001) and 5,969,071 (1999) to Matzinger, disclose phenolic rosin resins useful in lithographic printing inks. The resins of Matzinger were prepared without the addition of antifoaming agents and with a reduction in the emission of aldehyde vapors compared to that commonly known in the art.
European Patent No. EP 1 054 028 (2000), to Matzinger, provides hydrocarbon/acrylic hybrid resins for adhesives, inks, and coating compositions. Dicyclopentadiene is a necessary component for the resin compositions disclosed.
U.S. Pat. No. 5,498,684 (1996), to Bender, provides rosin-based phenolic resins as binders for ink formulations. The Bender resins reportedly remain stable after at least six months of continuous air exposure.
Production cost is an important consideration in the preparation of rosin-based ink binders. It is well known to those experienced in the art that the natural resins and resin acids normally utilized in the production of printing inks are a relatively expensive component of the ink binder. This expense is further compounded by the realization that the global supply of natural rosin is rapidly decreasing.
Health hazard is another important consideration in the preparation of rosin phenolic ink binders. It is well-known in the art to incorporate alkylphenol, particularly nonylphenol, as a component in preparing certain rosin-based ink binders. However, recent literature abounds with reports of possible adverse endocrine disruption effects to humans, domesticated animals, and wildlife, resulting from the release of nonylphenol and other alkylphenols into water sources (see, e.g., T. Sweeney, “Is Exposure to Endocrine Disrupting Compounds During Fetal/Post-Natal Development Affecting the Reproductive Potential of Farm Animals?” Domest. Anim. Endocrinol., vol. 23, pp. 203-209 (2002); C. Sonnenschein and A. M. Soto, “An Updated Review of Environmental Estrogen and Androgen Mimics and Antagonists,” J. Steroid Biochem. Mol. Bio., vol. 65, pp. 143-150 (1998)). In addition to the effect of these phenolic compounds on overall human and animal health, these findings could ultimately cause the cost of alkylphenols, and specifically nonylphenol, to increase dramatically as commercial manufacturers continue to move away from producing these chemicals, thereby diminishing global supply. In a worst-case scenario nonylphenol could even be banned altogether.
The present invention addresses the problems associated with the use of alkylphenols in the preparation of rosin-containing ink resins, and provides further related advantages as described herein.